Loader Node Memory Usage

[RADSr]

This may be a basic question - and if so I will be happy to get that step of my learning curve out of the way  😉 

If I have no schemas being loaded what is this memory being used for? ( screen cap )     Does the loader node just kind of keep in in cache until the next schema is loaded?   I did start another schema load and it didn't move the needle one way or the other so... guessing no on the previous question?

Selecting "details" confirms the memory usage but no further information on what the various tables and joins are *doing* with that memory.

I completely get memory usage during the load process, I'm just not sure what loader node memory is doing when there are no loads active.